Many lines of evidence attest to a multifactorial pathogenesis of diabetic complications in humans and in animal models of diabetes. Increased sorbitol pathway metabolism and non-enzymatic glycation products have been implicated by many investigators in the pathogenesis of vascular and neural dysfunction as well as early vascular structural changes changes in animal models of diabetes. The present studies were undertaken to assess the mechanisms that mediate vascular dysfunction associated with these biochemical imbalances. Three different animal models of diabetes were used: (1) rats with diabetes induced by injection of streptozotocin; (2) non-diabetic rats with acute hyperglycemia of 5 h duration induced by i.v. glucose infusion at a rate sufficient to produce plasma glucose levels comparable to in diabetic rats; and (3) the skin chamber granulation tissue model in which vessels in the chamber are exposed to buffer containing 5 or 30 mM glucose +/- pharmacological agents or 0.1 uM glycated rat serum albumin +/- pharmacological agents. Vascular function was assessed by injection of 11.3 m 46Sc microspheres for quantification of blood flow and by injection of [125I] and [131I]bovine serum albumin for quantification of vascular albumin permeation. Vascular dysfunction induced by elevated glucose levels in all three models was prevented by inhibitors of sorbitol pathway metabolism, inhibitors of nitrix oxide synthesis and inhibitors of prostaglandin synthesis. In the skin chamber model vascular dysfunction induced by elevated glucose levels and by glycated rat serum albumin was prevented by superoxide dismutase, probucol and inhibitors of nitric oxide synthase. These observations suggest that vascular dysfunction induced by increased sorbitol pathway metabolism and by products of non-enzymatic glycation is mediated by a common final pathway consistent with a scenario in which: increased superoxide production leads to increased intracellular calcium leveles, which leads to increased nitric oxide synthesis, which leads to increased blood flow and increased vascular permeability.